OpenCPN supports the use of MBtiles (v5.0.0).
Sat2Chart can make either KAPs or mbTiles. KAPs are a MapMedia format that's been around for years, and we've been using them since 2015. MbTiles are a newer database based format for storing map‑tiles. KAPs are limited to 128 separate colors, much like the old CompuServe GIFs. This turns out to be important when scrutinizing a coastline looking for minute differences in the shade of blue that might show an anchorage. MbTiles don't have a color limit, so the color quality is much better. And mbTiles have other advantages…
KAPs are essentially a single picture, taken from whatever altitude you choose. For OpenCPN to display this image at a different altitude (zoom level) it has to decide which pixels to keep and which to throw out. This can put a huge strain on its display engine, especially when panning around with many KAPs displayed. So much so that we typically switch to our CM93 charts when we want to pan to somewhere else, and then switch back to our KAPs only when we're displaying our new area of interest.
MbTiles, on the other hand, can have multiple zoom levels stored in the single file. This makes it easy for OpenCPN, as all it has to do is extract the correct zoom level from the mbTile and slam it out to the display engine. We find panning with mbTiles displayed is slightly slower than with our CM93 charts, but not badly so, and we're quite happy moving around with mbTiles displayed.
These are great MBtile Resources and we encourage others to add their mbtile downloads.